Properties

Pathogenesis

Clinical findings

Laboratory diagnosis

Treatment & Prevention

Short Gram-positive rod.

Beta hemolytic colonies grow aerobically on blood agar.

Multiply in cold conditions.

Motile.

Transmission:

- contact with animals or their feces.

- unpasteurized milk.

- contaminated vegetables.

Invasion of mononuclear phagoycytic cells.

Grows intracellularly.

Listerolysin O produces holes in cell membranes.

Diseases:

- meningitis

- sepsis

Occurrence in newborns & immunocompromised adults.

Infection during pregnancy can cause:

- abortion.

- premature delivery.

- stillbirth.

- severely ill baby with multisystem infection.

Newborns infected at time of delivery can have acute meningitis 1-4 weeks later.

Infections in other patients:

- there is usually underlying immunosuppression.

- patients most often present with meningitis.

- involvement of cerebral cortex occurs & this may lead to focal signs.

- pure encephalitis/brain abscess in absence of meningitis is rare.

Examination of CSF culture & blood culture.

Gram stain & culture:

- appearance of rods resembling diptheroids.

- formation of small, gray colonies with a narrow zone of beta-hemolysis on a blood agar.

Ampicillin with or without gentamicin.

Trimethoprim-sulfamethoxazole

Resistant to all cephalosporins.